Gamma-ray Burst 070707

(All information courtesy of the instrument teams.)

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Sat 07 Jul 07 16:09:17 UT
NOTICE_TYPE:    INTEGRAL Wakeup
TRIGGER_NUM:    4647,   Sub_Num: 0
GRB_RA:         267.8446d {+17h 51m 23s} (J2000),
                268.0493d {+17h 52m 12s} (current),
                266.4834d {+17h 45m 56s} (1950)
GRB_DEC:        -68.9104d {-68d 54' 36"} (J2000),
                -68.9119d {-68d 54' 42"} (current),
                -68.8966d {-68d 53' 47"} (1950)
GRB_ERROR:      3.12 [arcmin, radius, statistical only]
GRB_INTEN:      9.23 [sigma]
GRB_TIME:       58120.55 SOD {16:08:40.55} UT
GRB_DATE:       14288 TJD;   188 DOY;   07/07/07
SC_RA:          299.23 [deg] (J2000)
SC_DEC:         -76.83 [deg] (J2000)
SUN_POSTN:      106.47d {+07h 05m 52s}  +22.57d {+22d 34' 28"}
SUN_DIST:       132.33 [deg]   Sun_angle= -10.8 [hr] (East of Sun)
MOON_POSTN:      12.35d {+00h 49m 23s}   +8.64d {+08d 38' 27"}
MOON_DIST:      103.18 [deg]
GAL_COORDS:     324.64,-20.03 [deg] galactic lon,lat of the burst
ECL_COORDS:     268.89,-45.48 [deg] ecliptic lon,lat of the burst
COMMENTS:       INTEGRAL GRB Coordinates.  
COMMENTS:       Possibly real GRB event

red DSS finding chart ps-file

GCN NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Sat 07 Jul 07 16:12:18 UT
NOTICE_TYPE:    INTEGRAL Refined
TRIGGER_NUM:    4647,   Sub_Num: 1
GRB_RA:         267.8005d {+17h 51m 12s} (J2000),
                268.0051d {+17h 52m 01s} (current),
                266.4399d {+17h 45m 46s} (1950)
GRB_DEC:        -68.8945d {-68d 53' 39"} (J2000),
                -68.8960d {-68d 53' 45"} (current),
                -68.8805d {-68d 52' 49"} (1950)
GRB_ERROR:      3.05 [arcmin, radius, statistical only]
GRB_INTEN:      9.78 [sigma]
GRB_TIME:       58126.50 SOD {16:08:46.50} UT
GRB_DATE:       14288 TJD;   188 DOY;   07/07/07
SC_RA:          299.23 [deg] (J2000)
SC_DEC:         -76.83 [deg] (J2000)
SUN_POSTN:      106.47d {+07h 05m 53s}  +22.57d {+22d 34' 28"}
SUN_DIST:       132.34 [deg]   Sun_angle= -10.8 [hr] (East of Sun)
MOON_POSTN:      12.37d {+00h 49m 30s}   +8.65d {+08d 39' 16"}
MOON_DIST:      103.22 [deg]
GAL_COORDS:     324.65,-20.01 [deg] galactic lon,lat of the burst
ECL_COORDS:     268.87,-45.46 [deg] ecliptic lon,lat of the burst
COMMENTS:       INTEGRAL GRB Coordinates.  
COMMENTS:       Possibly real GRB event

GCN Circular #6605
V. Beckmann, C. Ricci, M. Beck (ISDC, Versoix), S. Mereghetti, A. Paizis (IASF-Milano), D. Gotz (CEA-Saclay), and J. Borkowski (CAMK, Torun) on behalf of the IBAS Localization Team report:
A GRB lasting about 100 s has been detected by IBAS in IBIS/ISGRI data on July 7 at 16:08:21 UT.
The coordinates (J2000) are:
```
RA:  267.67 [degrees]
DEC: -68.95 [degrees]
```
with an uncertainty of 4 arcmin. The light curve is a single, FRED-like peak. This message can be cited.

GCN NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Sat 07 Jul 07 22:41:45 UT
NOTICE_TYPE:    INTEGRAL Offline
TRIGGER_NUM:    4647,   Sub_Num: 2
GRB_RA:         267.6699d {+17h 50m 41s} (J2000),
                267.8748d {+17h 51m 30s} (current),
                266.3073d {+17h 45m 14s} (1950)
GRB_DEC:        -68.9500d {-68d 56' 59"} (J2000),
                -68.9516d {-68d 57' 05"} (current),
                -68.9353d {-68d 56' 06"} (1950)
GRB_ERROR:      4.00 [arcmin, radius, statistical only]
GRB_INTEN:      9.78 [sigma]
GRB_TIME:       58126.50 SOD {16:08:46.50} UT
GRB_DATE:       14288 TJD;   188 DOY;   07/07/07
SC_RA:          299.23 [deg] (J2000)
SC_DEC:         -76.83 [deg] (J2000)
SUN_POSTN:      106.75d {+07h 06m 59s}  +22.54d {+22d 32' 42"}
SUN_DIST:       132.20 [deg]   Sun_angle= -10.7 [hr] (East of Sun)
MOON_POSTN:      15.84d {+01h 03m 21s}  +10.38d {+10d 22' 55"}
MOON_DIST:      106.09 [deg]
GAL_COORDS:     324.58,-19.99 [deg] galactic lon,lat of the burst
ECL_COORDS:     268.81,-45.52 [deg] ecliptic lon,lat of the burst
COMMENTS:       INTEGRAL GRB Coordinates.  
COMMENTS:       refined_coordinates_after_offline_analysis

GCN Circular #6606
V. Beckmann, C. Ricci, M. Beck (ISDC, Versoix), S. Mereghetti, A. Paizis (IASF-Milano), D. Gotz (CEA-Saclay), and J. Borkowski (CAMK, Torun) on behalf of the IBAS Localization Team report:
A GRB lasting about 100 s has been detected by IBAS in IBIS/ISGRI data on July 7 at 16:08:21 UT.
The coordinates (J2000) are:
```
RA:  267.67 [degrees]
DEC: -68.95 [degrees]
```
with an uncertainty of 4 arcmin. The light curve is a single, FRED-like peak. This message can be cited.
GCN Circular #6607
D. Gotz (CEA Saclay), V. Beckmann (ISDC, Versoix), S. Mereghetti, and A. Paizis (IASF, Milano) on behalf of the IBAS localization Team report:
A refined analysis of GRB 070707 shows that it is composed by a single spike lasting about 1.1 s, and its spectrum can be well fit with a power law of slope 1.4, indicating a rather hard spectrum.
Its refined position is
```
R.A. (J2000): 267.7506 [degrees]
DEC. (J2000): -68.9144 [degrees]
```
with an uncertainty of 2.1 arcmin (90% c.l.)
This messages can be cited.
GCN Circular #6608
D. Gotz (CEA Saclay), V. Beckmann (ISDC, Versoix), S. Mereghetti, and A. Paizis (IASF, Milano) on behalf of the IBAS localization Team report:
A refined analysis of GRB 070707 shows that it is composed by a single spike lasting about 1.1 s, and its spectrum can be well fit with a power law of slope 1.4, indicating a rather hard spectrum.
Its refined position is
```
R.A. (J2000): 267.7506 [degrees]
DEC. (J2000): -68.9144 [degrees]
```
with an uncertainty of 2.1 arcmin (90% c.l.)
This messages can be cited.
GCN Circular #6609
P. D'Avanzo (INAF-OABr), S. Piranomonte, L. Stella (INAF-OAR) and G. Chincarini ((INAF-OABr) report on behalf of the MISTICI collaboration:
We observed the field of the short GRB 070707 (Beckmann et al., GCN 6605; Gotz et al., GCN 6607) using FORS1 on the VLT telescope about 11 hours after the trigger time. We obtained 20 minutes of R-band imaging.
Inside the refined INTEGRAL error circle (Gotz et al., GCN 6607) we do not detect any obvious afterglow candidate down to the depth of the DSS image. Our 3-sigma limiting magnitude is R=25.7.
Further observations are planned. We acknowledge the ESO staff for reliable support.
This message can be cited.
GCN Circular #6610
A.P. Beardmore, K.L. Page (U. Leicester) and A. Parsons (GSFC) report on behalf of the Swift XRT team:
On 2007 Jul 08 00:57:50UT the Swift XRT started observing the field of the INTEGRAL burst GRB 070707 (Beckmann et al., GCN 6606; Gotz et al., GCN 6607). In a 3.8ks exposure photon counting mode image taken from 31.8 ks to 54.1 ks after the trigger, we detect a source at RA, Dec = 267.7437, -68.9242, which is
```
RA(J2000)  =  17h 50m 58.49s
Dec(J2000) = -68d 55m 27.0s
```
with an uncertainty of 5.4 arcsec (90% containment). This is 36.3 arcsec from the position reported by Gotz et al. (GCN 6607), and within their error circle.
Using a circular extraction region of 10 pixels radius, we observe 26 total counts. Together with an estimated background level of 1.0 count in the extraction region, we find the 99.73% Bayesian confidence level on the source count rate is 0.003 to 0.011 count s^-1.
However, with such a limited number of photons, it is impossible to say at this stage whether the source is fading and if this is the X-ray counterpart to the GRB.
This circular is an official product of the Swift XRT team.
GCN Circular #6611
P. Schady (MSSL-UCL) and A. Parsons (GSFC) report on the behalf of the Swift UVOT team:
The Swift/UVOT observed the field of INTEGRAL burst, GRB070707 starting 8.8hrs after the INTEGRAL trigger (Beckmann et al. 2007, GCN Circ. 6606). We do not find any new source in any of the UVOT observations inside the refined INTEGRAL error circle (Gotz et al. 2007, GCN Circ. 6607) or XRT error circle (Beardmore et al. 2007, GCN 6610)
The 3-sigma upper limits for detecting a source inside the refined XRT error circle in the initial data products are:
```
Filter    T_mid(s) Exp(s) Mag (3-sigma upper limit)
-------------------------------------------------------
V         53885    543      19.7
B         31910    324      20.6
U         47905    97       19.5
UVW1      47149    964      20.3
UVM2      39328    1190     20.5
UVW2      53182    1800     20.5
-----------------------------------------------------------------
```
where T_mid is the weighted mid time of the coadded exposure. The values quoted above are not corrected for the expected Galactic extinction corresponding to a reddening of E_{B-V} = 0.08 mag in the direction of the burst (Schlegel et al. 1998).
GCN Circular #6612
S. Piranomonte (INAF-OAR), S. Vergani (DIAS-DCU), P. D'Avanzo & G. Tagliaferri (INAF-OABr) report on behalf of the MISTICI collaboration:
Following the detection by Swift/XRT (Beardmore et al., GCN 6610) of GRB 070707 (Beckmann et al., GCN 6605; Gotz et al., GCN 6607), we have inspected our VLT R-band images (D'Avanzo et al., GCN 6609).
Inside the XRT error box, we find a single source with R ~ 23.0 (calibrated using archival instrumental zeropoints), at the coordinates (J2000, 0.5" error):
```
RA(2000) = 17:50:58.55
Dec(2000) = -68:55:27.2
```
At the present stage, we cannot yet assess the relationship of this source with GRB 070707. Further observations are planned.
This message can be cited.
GCN Circular #6613
P. D'Avanzo (INAF-OABr), S. Piranomonte (INAF-OAR) & S. Vergani (DIAS-DCU) on behalf of the MISTICI collaboration L. Christensen, P. Amico (ESO) report:
We observed again the field of the short/hard GRB 070707 (Beckmann et al., GCN 6605; Gotz et al., GCN 6607) with the ESO-VLT in imaging mode. Observations have been carried out around Jul 09.08 UT in the R band with the FORS1 camera.
A comparison with the images of our previous observing run (D'Avanzo et al., GCN 6609) revealed that the object inside the XRT error box (Beardmore et al., GCN 6610) reported by Piranomonte et al. (GCN 6612) faded of about 0.7 +/- 0.1 mag. We thus propose this object as the optical afterglow of GRB 070707.
Further observations are planned. We acknowledge the ESO staff for reliable support.
This message can be cited.
GCN Circular #6615
S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and T. Cline on behalf of the Konus-Wind team report:
The short GRB 070707 (Beckmann et al., GCN 6605; Gotz et al., GCN 6607) triggered Konus-Wind at T0=58122.823 s UT (16:08:42.823).
The Konus-Wind light curve shows a multipeaked structure with a total duration of ~1 s. As observed by Konus-Wind the burst had a fluence of 1.41(-1.07, +0.16)x10^-6 erg/cm2, and a 16-ms peak flux measured from T0-0.016 s 8.1(-6.7, +2.9)x10^-6 erg/cm2/s (both in the 20 keV - 2 MeV energy range).
The spectrum of the most intense part of the burst (from T0 to T0+0.256) is well fitted (in the 20 keV - 2 MeV range) by a power law with exponential cutoff model: dN/dE ~ E^(-alpha)*exp(-E*(2-alpha)/Ep) with alpha = 0.57 (-0.59, +0.43) and Ep = 427(-144, +374) keV (chi2 = 13/19 dof). Thus, this burst is classified as a short hard GRB.
All the quoted errors are at the 90% confidence level.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.rssi.ru/LEA/GRBs/GRB070707_T58122/
GCN Circular #6626
A.P. Beardmore (U. Leicester) and A. Parsons (GSFC) report on behalf of the Swift-XRT team:
The Swift XRT obtained further follow-up observations of GRB 070707 (Beckmann et al., GCN 6606; Gotz et al., GCN 6607). In an 11.1 ks exposure photon counting mode image taken from 325.1 ks to 516.6 ks after the trigger, and using the same 10 pixel radius extraction region as before, we find a 3 sigma upper limit to the observed count rate of 0.0011 count/s. When compared with the initial XRT detection (Beardmore et al., GCN 6610) of 0.0066 +/- 0.0013 count/s (where the error bar is a 1 sigma estimate) we conclude the source has faded and that it was the X-ray counterpart to the GRB.
An absorbed powerlaw fit to the photon energy distribution of the source observed during the first XRT observation (from 31.8 ks to 54.1 ks after the trigger), using Cash statistics and with the NH fixed at the (Dickey and Lockman) galactic value of 6e20cm^-2, gave a powerlaw index of 2.7 +/- 0.6. The observed 0.3-10 keV flux was (2.4 +2.0 -1.4)e-13 ergs cm^-2 s^-1.
This circular is an official product of the Swift-XRT team.
GCN Report 75.1
GCN_Report 75.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_75_1.pdf by A. Parsons at GSFC titled: "Final Swift observations of INTEGRAL GRB 070707"
0805.2880from 19 May 2008
McGlynn: GRB 070707: the first short gamma-ray burst observed by INTEGRAL
Abstract: INTEGRAL has observed 47 long-duration GRBs (T_90 > 2s) and 1 short-duration GRB (T_90 < 2s) in five years of observation since October 2002. This work presents the properties of the prompt emission of GRB 070707, which is the first short hard GRB observed by INTEGRAL. The spectral and temporal properties of GRB 070707 were determined using the two sensitive coded-mask gamma-ray instruments on board INTEGRAL, IBIS and SPI. The T_90 duration was 0.8s, and the spectrum of the prompt emission was obtained by joint deconvolution of IBIS and SPI data to yield a best fit power-law with photon index alpha = -1.19 +0.14 -0.13, which is consistent with the characteristics of short-hard gamma-ray bursts. The peak flux over 1 second was 1.79 photons/cm^2/s and the fluence over the same interval was 2.07 x 10^-7 erg/cm^2 in the energy range 20-200keV. The spectral lag measured between 25-50keV and 100-300keV is 20 +/- 5ms, consistent with the small or negligible lags measured for short bursts. The spectral and temporal properties of GRB 070707 are comparable to those of the short hard bursts detected by other gamma-ray satellites, including BATSE and Swift. We estimate a lower limit on the Lorentz factor Gamma >~ 25 for GRB 070707, assuming the typical redshift for short GRBs of z=0.35. This limit is consistent with previous estimates for short GRBs and is smaller than the lower limits of Gamma >~ 100 calculated for long GRBs. If GRB 070707 is a member of the recently postulated class of short GRBs at z ~ 1, the lower limit on Gamma increases to Gamma >~ 35.
0807.1348 from 8 Jul 2008
Piranomonte: The short GRB070707 afterglow and its very faint host galaxy
Abstract: We present the results from an ESO/VLT campaign aimed at studying the afterglow properties of the short/hard gamma ray burst GRB 070707. Observations were carried out at ten different epochs from ~0.5 to ~80 days after the event. The optical flux decayed steeply with a power-law decay index greater than 3, later levelling off at R~27.3 mag; this is likely the emission level of the host galaxy, the faintest yet detected for a short GRB. Spectroscopic observations did not reveal any line features/edges that could unambiguously pinpoint the GRB redshift, but could set a limit z <~ 2.5. In the range of allowed redshifts, the host has a low luminosity, comparable to that of long-duration GRBs. The existence of such faint host galaxies suggests caution when associating short GRBs with bright, offset galaxies, where the true host might just be too dim for detection. The steepness of the decay of the optical afterglow of GRB 070707 challenges external shock models for the optical afterglow of short/hard GRBs. We argue that this behaviour might results from prolonged activity of the central engine.

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Jochen Greiner, last update: 14-Jul-2008 [Disclaimer]